Dielectric materials are widely used in semiconductor processing. One of the most commonly used dielectric materials is SiO2 due to its exceptional physical and electrical properties. Further, SiO2 is efficient to use as it may be directly formed on a silicon wafer in an oxidizing ambient. However, as semiconductor processes continue to advance and device geometries are further reduced, SiO2 may no longer be an adequate dielectric material. In this regard, SiO2 has a dielectric constant of 3.9, which is too low to meet the electrical requirements of advanced semiconductor manufacturing processes. For example, gate leakages for SiO2 are prohibitive to its use in advanced, high-speed semiconductor logic and memory processes.
Given the above, alternative metal oxide based dielectric materials are currently being evaluated as SiO2 replacements. Such dielectric materials have relatively high dielectric constants (k-values) in the range of approximately 10 and higher, and may contain elements such as yttrium (Y), lanthanum (La), zirconium (Zr), and hafnium (Hf), among others. Such dielectrics materials typically take the form of oxides of one more such elements, for example, and may be termed high-k dielectrics.
Dielectrics containing such elements, however, must be deposited on a semiconductor wafer, rather than being formed directly on a silicon substrate, as with SiO2. Thus, the final electrical properties of a dielectric layer or stack of dielectric layers comprising such materials depends on a number of factors, such as the particular material or materials chosen to form the dielectric layer(s), the method of deposition, the sequence of deposition if mixed oxides are deposited, the preparation of the Si surface prior to deposition, any thermal treatment that is performed after deposition, among other considerations.
Based on the foregoing, high-k dielectric compositions that can be deposited on semiconductor substrates that are further processed, where the dielectric layers exhibit electrical and physical properties comparable or superior to SiO2 is desirable. Such materials would provide considerable benefits to the semiconductor industry through their use. For example, one of the major advantages of such materials would be a reduction in gate leakage, as the higher k values would allow the use of physically thicker layers without resulting in any significant loss of gate capacitance, thereby reducing gate leakage. Such high-k dielectric materials may be used as gate dielectrics to manufacture transistors for future CMOS high-speed logic circuits and/or to manufacture capacitors for certain memory device applications. Thus, such high-k dielectrics would significantly facilitate the scaling of semiconductor based electronic devices in future logic and memory technologies.